The invention relates to a method of removing material from a part of a plate which is suitable for powder blasting by means of a powder-blasting technique, using a blasting mask.
Removing material may be understood to mean, for example, the provision of cavities and/or apertures, but also a process of cutting shapes (for example, discs) by way of powder blasting. The cavities may be, for example, slots, pits or grooves. Plates which are suitable for powder blasting are particularly made of hard, brittle materials such as glass or ceramic material (for example, ferrite, a sintered oxidic ferromagnetic material). The plates may be made of an insulating material (for example, glass), an electrically conducting material (for example, some types of ferrite) or a semiconducting material (for example, silicon and some types of ferrite). These types of plates are particularly used in flat lamps, meander lamps, TL lamps, luminescent gas discharge displays such as plasma displays, field emission displays, cathode ray tube displays and electron duct displays in which electrons are propagated in ducts having walls of insulating material in which the apertures and/or cavities are used for manipulating electron currents. They may be formed, for example, as control plates provided with addressable electrodes, as transport plates in which parallel cavities constitute ducts, and as spacer plates which may be placed, for example, between a control plate and a luminescent screen in a luminescent display.
A metal blasting mask is generally used in this method. The pattern to be blasted is defined in this blasting mask. Such a method is known from U.S. Pat. No. 5,593,528.
The use of a metal blasting mask has the drawback that it is expensive, while it can generally be used only once. Another drawback is the deformation of the metal due to the force of the abrasive powder particles. Consequently, the blasting mask may get detached during blasting, resulting in underblasting.